Butterfly wing color has largely nano-structural origins. Structural coloration produces more intense colors than chemical pigmentation alone. The Morpho’s structural blue is visible from 2 miles, and the blue can be optimized if their nanostructures were spaced closer. However, these nanostructures do more than produce color, such as regulating heat, which prevents them from being color-optimized. Iridescence can be produced from a combination of structural and pigmental color. Some butterflies overlay blue iridescence over yellow pigment, changing between blue, yellow and green. Structural color alone can also produce iridescence. Polarized iridescence, visible-light iridescence, and UV iridescence are seen in different butterfly species. Polarized and UV iridescence allow for intraspecific signaling. Different modes of producing iridescence through primarily coherent scattering of light are seen through thin-film interference, diffraction gratings, and photonic crystals, discussed in detail. I modeled thin-film interference through oil-spills and the teflon-coating on anti-reflective prescription glasses. I modeled photonic crystals through penrose tiles and the concept of aperiodic and periodic tiling in general. I observed that different butterflies have different ranges of iridescence, with some varying between many colors while others varied between a few and sought to find reasons for that. I found that the range of iridescent colors exhibited is affected by the thickness, shape, and spacing of material at each layer in the case of thin-film interference. Generally, crystal-like and laminar structures--structures with long range order at the nano-level, often give rise to strong iridescence while quasi-ordered nanostructures either produce weak iridescence or none at all.